The present invention relates to a feedback control system for internal combustion engines in accordance with the oxygen concentration of the exhaust emissions to maintain the air-fuel ratio of the mixture supplied to the engine at a desired point.
An oxygen sensor of the type wherein the sensor is biased to generate a linearly varying saturation current is shown and described in Japanese Laid-open Patent Applications Nos. 57-192852 and 57-192854. This type of oxygen sensor is advantageous in that it enables detection of the oxygen concentration of exhaust emissions from an internal combustion engine as a linear indication of the air-fuel ratio of the mixture supplied thereto when it is leaner than stoichiometric. A mixture control system employing the biased oxygen sensor is disclosed in Japanese Laid-open Patent Application No. 58-20950.